docs: def get_preflist(self, bucket, key):
          """
          Get the preflist for a bucket/key
  
          :param bucket: Riak Bucket
          :type bucket: :class:`~riak.bucket.RiakBucket`
          :param key: Riak Key
          :type key: string
          :rtype: list of dicts
          """
          if not self.preflists():
              raise NotImplementedError("fetching preflists is not supported.")
          msg_code = riak.pb.messages.MSG_CODE_GET_BUCKET_KEY_PREFLIST_REQ
          codec = self._get_codec(msg_code)
          msg = codec.encode_get_preflist(bucket, key)
          resp_code, resp = self._request(msg, codec)
          return [codec.decode_preflist(item) for item in resp.preflist]